Semen quality and libido of rams of different mutton breeds in the summer months

SEMEN QUALm AND LIBIDO OP RAl-IS OF DIFFEBEOT I-50TT0N BREEDS

THE Smmfi MONTHS

by

TED H. DOAJIB

B» S,, Oklahoma Agricultural and Mechanical College,
Stillwater i Ofclahotoa, 1952

A THESIS

submitted in partial fulfilliaent of the

requirements for the degree

MASTER OS' SCIENCE

Department of ..\nlmal Husbandry

KANSAwS STATE COLLEGE
OP AGHICTJLTUR3 AIJD APPLIED SGIENCB

1953

Docu-
ment

ii

TABLE 01? COKTEOTS

Q IIITRODUCTION 1

LITERATURE REVIEW 2

BXPr-RE'ElITAL PROCEDURES , ^

Animals Used , , . , , , ?

ISathods of Determining Valuation of Libido... ?

Collection of Seosen. ♦ . . . .Il2

Method of Determining Motility.. ..17

Method of Counting Spero^ 17

EXPERIMENTAL RESULTS 21

SUMMARY AIJD CONCLUSIONS. . , 28

AC:aiO\\CLEDGEMEira .30

LITSRATURB CITED ...31

APP3I\[DIX 32

m

PRODUCTION

Sheep production has been an important livestock production
enterprise in the United Str.tes for many years. Ranchers and
farmers have made many changes in production methods during this
time to make it more profitable.

Lamh production is influenced to a large extent by the
reproductive efficiency of the males and females; therefore, it
is very important that the sheep raiser know more about the nor-
mal reproductive process of sheep so he can secure maximum lamb
crops.

Most breeds of sheep breed only during late summer and fall.
Breeding at this time permits the birth of lambs from December
to March and even on into the sumrcer months. Many farmers and
ranchers in Kansas and other parts of the United States prefer
that lambs be dropped as early in the fall as possible so the
lambs will be larg:e enough to sell before the hot season starts
in late spring and sunmer. The top seasonal market prices are
generally obtained in early spring and late winter. Early
lambing is essential If these are to be obtained. Kany pure-
bred sheep breeders prefer fall lambing with part of the flock
because it facilitates the use of young males for sale, showing,
and breeding.

Since the gestation period of the domesticated sheep, genus
Ovis, is approximately 150 days, the ewes must be bred in May,
June, or July in order to produce lambs early enough to be

2

benefited by more favorable climatic conditions for growth as well
as a high market price*

It has not been clearly demonstrated vrtiethcr it Is entirely

«

the fault of the ewes if they fail to produce early lambs. Rams
may also bo responsible if there is a decline in their fertility
during surrjner months. One of the purposes of this experiment
was to study reproductive potency of the racs of mutton breeds
during the season of the year when ewes must be bred to produce
fall lambs.

The other purpose of this experiment i/as to compare the
reproductive potency of different breeds of rams. This infor-
mation would help the commercial breeder to select a breed that
has a high breeding efficiency during the summer months, and thus
enable him to secure a higher lambing percentage during the
fall lambing season.

LITERATURE REVIEW

Ifeny farmers and ranchers x/ho raise sheep In Kansas and
the Southwestern States assume that rams of mutton breeds are
poor breeders during the summer months of June and July because
cf the seasonal high temperature.

According to Rice and Andrews (6), high environmental
temperatures may cause temporary sterility, and perhaps a perma-
nent sterility, if the temporature of the testis is elevated
above the body temperature ^./hlch is approximately 105*^ P.

1

The testes are very sensitive to temperature changes; and if
the scrotum cannot maintain these organs at the optimum tempera-
ture which is 102° F,, there Is a physiological disturbance of
normal spermatogenesis \jt\lQh results in the i^roduction of poor
quality semen. The fertility of the ram is also narkedly re-
duced. An atmospheric temperature of 110°-ll5^ F. may raise
the scrotal temperature to a point at vrhich it is detrimental
to normal spermatogenesis. The scrotuia is an efficient thermal
regulator in the presence of environmental temperatures lower
than 102*^ P.

The insulation provided by the covering of wool on the
scrotum and the natural position of the scrotum, which is near
coolness of the ground on humid days, provide considerable
protection against high temperatures. Another factor which aids
In preventing complete sterility is the normal cooling at nl^ts.

I'lcKenzle and Berliner (2) studied semen qualities of
Hampshire and Shropshire rams in Missouri and reported that
spermatogenesis was continuous during all months of the year,
but noted that there were definite seasonal trends In the quality.
The Hampshires appeared to have a maximum semen quality from
August to January and that for the Sbropshires ranged from
October to January. A pronounced reduction in semen quality
prevailed during the months of July and August.

According to Moore and Quick (k) y the temperature in the
scrotum is much lower than that of the peritoneal cavity and

found that tho difference betwoen the temperature of these
two positions changed as the temperature of the external envi-
ronment varied.

Rams possessing a large breedinj? capacity generally dis-
play a very active libido. There are several factors which
affect the sex drive of a male. The greatest handicap of mutton
rams is an excessive amount of fat. McKenzie and Phillips (3)
state that rams in high condition are sluggish and unwilling to
hread on decisively warm days* The mutton rams have a tendency
to become fat more readily than other types of rams 5 therefore,
the ration of mutton rams should be observed more closely.

Libido and sexual activity are very similar, and it is very
important to know if rams have the abilit;>^ to find an estrous
ewe. A ram should also be able to make several breeding services
a day over an extended period of time. McKenzie and Berliner (2)
concluded that an average of five successive mounts by a ram
during a ten-minute period was indicative of excellent libido.

Sperm motility is a very good indicator of fertility. If
a ram does not have active sperm, his qualities as a breeder are
poor. Schott and Phillips (7) found that the rate of movement
of the noriaal sperm is very rapid. '#ien placed in a proper
media, raammali?. spermetazoa v/ere noted to move from 1-^ mm per
minute, v/ith ac average of 3 mm per minute. Phillips and Andrews
(5) found ram sperm in the ovarian bursa (funnel) of the ewe
30 minutes after copulation.

EXPERIKEKDAL PROCEDORES

Animals Used

The sinimals used for this experiment; v;ere nine purebred
stud rams of Kansas State Collese (Plates 1, 2| and 3)» The
groups included three Hampshires, three Shropshires, two South-
do-wns, and one Suffolk, They were fed the basic ration consist-
ing of one-half oats, one fourth bran, and one-fourth corn at
the rate of one pound per ram per day. Tlio roughage was sudan
pasture. The rams were housed in the college sheep barn during
the summer of 1952 which was unusually hot and dry.^

At the beginning of the experisiental period, tiro barren
ewes were injected with a natural estrogenic hormone, Estrone,
and the rams were permitted to mount them in a normal manner*
A specially constructed chute (Plate Fig, 1) retained the
females relatively motionless during breeding or collection of
semen. The rams became less timid after a series of preliminary
mounts were accomplished.

Methods of Deteraining Valuation of Libido

The breeding activity of all rama vas observed and recorded
so that comparisons could be made, A series of ratings v/ere
used to classifjr- all rams. Libido way rated as "excellent" if
the ram mounted and served a owe prompt lyj libido was rated as

1, Average daily temperature 92°, average monthly rainfall 1/2"
to compare with the ten-year average temperature 800,
rainfall 2". '

EXPLMATIOH OP PLATE I

Figure 1 Hampshire Ram nuDioer 1 3 years old
Figure 2 Hampshire Ran number 2 2 years old
Figure 3 Hampshire Ram number 3 1 year old

PLATE I

EXPLAHATIOK OP PLATE II

Figure 1 Suffollr. Ram
Figure 2 Soutbdo\jn Ram
Figure 3 SouthdoLU Ram

2 3''ears old
number 1 2 years old
number 2 h years old

9

PLATE II

EXPLMATIOlj OP PLATE III

Figure 1 Shropshire Rp.m number 1 1 ;rear old
Figure 2 Shropshire Rem number 2 2 years old
Figure 3 Shropshire Ran number 3 3 years old

11

PLATE III

"good" if he mounted and served within three minutes. Libido
was rated as "fair" if the ram mounted and served betv;een three
and five minutes. If the ram was uninterested, he was rated as
"poor". Breeding activity and libido of the rams was also ob-
served upon turning them into a flock of ewes to search and find
those in heat. The following ratings were given; if the ram
was eager in his efforts, he was rated as "good"; if he was slug
gish but attempted to search, he was given a "fair" rating; and
if he was entirely uninterested, he was classified as "poor"*

Collection of Semen

After the rams were familiar with breeding the ewes in the
chute, an artificial vagina (Plate 5) was used to collect the
semen. As the rams mounted the ewes, the penis v/as guided into
the artificial vagina.

The artificial vagina was made from a number 2 automobile
water hose (approximately six inches long) vrtiich was used as the
outer jacket and a section of rubber tubing of soft flexible ma-
terial as the inner lining. A valve was inserted in the outer
casing to enable the collector to regulate air pressure between
the layers (Plate 5, Fig. 1,). Water of approximately 110°-1200
was placed between the two tubings and enough air was forced
through the valve to produce satisfactory pressure for the rams.
A lubricant of an oil-base gelatin (KY Jelly) was used to ensure
free motion of the penis. A test tube was attached to the end

EXPLANATION OF PLATE IV

Figure 1 Chute constrncted for confinement of ewe.
Figure 2 Ewe confined to chute.

Figure 3 Ran approaching ewe in chute for collection.

EXPLMATION OF PLATS V

Figure 1 Unconatructed artificial vagina.

Figtrre 2 Equipment used to bring about estrous
and for collection of semen.

PLATE V

Fig. 2

17

of the inner lining by a funnel-shaped rubber tube to collect
the ejaculate (Plate 5, Fig. 2).

Method of Determining Motility

Sperm motility was observed by placing a drop of aeraen at
one end of a clean miscroscope slide. The drop of semen was
drawn across the first slide as to make an even film.

This smear was made immediately after the semen collection
to prevent the sperm from dying or becoming sluggish due to light,
temperature, and other mechanical disturbances. The slide was ex-
amined with a miscroscope under high pov;er for the rhipping and
movement of the sperm's tails. Motility was classified by num-
bers ranging from 1 to 5, with 5 indicating the greatest motility.
If wave movements were seen due to rapid whipping of tails, the
sample of semen was classified very high, number 5. If the tails
were moving a reasonably active speed, motility was rated good or
k. If the sperm were moving at a progressive movement limited to
individual sperm, it was rated fair by number 3. If they were
very sluggish and moving slowly, they were classified as poor or
2 J and if the sperm were dead, they were rated as 1 which meant no
motility*

Method of Counting Sperm

A Hemecytometer (Plate VI) was used to make the sperm counts
as described by Bergman and Hewitt (1) for counting red blood
cells. The red blood cell diluting pipette and a diluting fluid

EXPLANATION OP PLA'^ VX

Equipcyant uaod for oouriUing of sperm and for determining

fpotllity of the gperm»

of 2^% sodium ci irate was used to make the semen dilution. The
technique used was to draw semen within the pipette up to the ,5
mark and then draw the diluting fluid into the pipette up to the
11 mark. After this step, the index finger and the thumb were
placed over each end of the pipette and shaken well until the liq-
uids were thoroughly mixed* A standard counting chamber was used.
After placing a cover slip of the region of the slide with the
marked area, a drop of diluted semen was placed at the edge of the
cover slip so it could flow under the cover slip. The counting
chamber was placed under high power objective of the microscope.
Five blocks were counted on the field of l6 squares. These were
the corners and the middle square of the field.

The sum of these squares equalled the number of sperm in 80
small squares. The small squares on the counting chamber covered
an area of one square nillimeter. Since each small square equalled
1/20 mm. square, it took ^0 squares to make a square millimeter.
Eighty squares equalled 1/5 square ram. The depth of the counting
chamber was 1/10 mm. and the diluti on was 1/200. Hence, the num-
ber of the sperm in 8o small squares times 5 times 10 times 200
equalled the number of sperm per cubic millimeter of semen. There-
fore, 10,000 times 80 squares equalled the number of sperm per
cubic millimeter. To obtain the total number of sperm in one ejac-
ulation, the number of sperm per cubic millimeter was multiplied
times 100 and the product was multiplied times the volume of semen
the individual ejaculated.

21

EXPERIMENTAL RESULTS

The rams were ranked by breed and within "breeds for semen
quality and libido*

The breeding activity of the Hampshires and Suffolk in the
ewe flock was high regardless of the extreme temperature which
was witnessed during the collection period. The Southdowns and
Shropshires ranked "good" for breeding activity in the ewe flock.

The Suffolk and Hampshires ranked higher than the Shrop-
shires and Southdotms in regard to motility.

The Suffolk and Hampshires \/ere never below the "excellent"
rating (Table 1) for their breeding activity upon serving a ewe
with the exception of four times when the Suffolk vras rather tim-
id and one yearling Hampshire was still inexperienced. The other
exception was unexplainable •

The flock breeding activity of the Southdown and Shropshire
rams were very similar. One ram of each breed was very active
and one was rated "fair". This resulted in the t\iro breeds receiv-
ing a "good" rating. The ratings of the four breeds of rams could
be in two groups i "excellent" for the Hampshires and Suffolk, and
"good" for Shropshires and Southdowns. It should be noted that
the No. 3 Shropshire was ratea "fair" in breeding activity al-
though he was sterile.

The semen characteristics considered for its evaluation were
volume, number of sperm per cubic millimeter, total number of

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sperm per ejaculation and the motility of aperm (Table ?.)•

^lotility, which was ranked by nucibers, was highest in the
Hampshires and Suffolk. The Suffolk received the highest individ-
ual motility rating. Motility scores for the three Hampshire rams
showed considerable variability but on the average were higher
than the mean scores of the Southdovms and Sliropshires. The semen
from these two later breeds received an average motility rating
of "fair".

It vras found that the sperm count of the Suffolk was 800,000
more sperm i^r cubic millimeter than the next highest rated indi-
vidual \ihich was a Southdown. The Suffolk's average number of
sperm was ^-,180, 000 to the No. 1 Southdown's 3>312jOOO sperm/mm^.
The No. 1 axid Ko. 2 Hampshires were also rated high in total num-
ber of spf?rm with an average of 3>270,000 for seven collections
and 3,260,000 for eight collections respectively. The No. 3 Hamp-
shire, Ho. 2 Southdovai and Wo. 2 Shropshire had approximately the
same number of sperm per cubic millimeter of semen. The range
was from 2,890,000 to 3>503,000. The No* 1 Shropshire, while being
rated "excellent" in his activity and libido, had a comparative low
sperm count* His count averaged 1,870,000 sperm per mm^ of semen*
The No* 3 Shropshire produced only dead sperm j however, a sperm
count was taken and indicated from 1,350,000 to 3,625,000 sperm per
mm-** This indicated the continuous production of spermatozoa even
though the sperm were dead at the time of e;5aculation.

In the report by ItoKenzle and Berliner (2), the volume of
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a few exceptions to this volume range in the semen collections
in this study. In four collections, semen volumes ranged, from
2-2.50 cc. per ejaculation, but the average for the nine rams on
kk collections was 1 cc. The Suffolk surpassed all other individ-
ual with 1.625 cc. per collection. This vms at the time when he
was not being used for any breeding except for this experiment.
The exceptionally high volume of semen per ejaculation for this
ram may be explained to a certain extent because of the long in-
tervals between each collection. The reason for the long collec-
tion intervals was because he often became timid or frightened,
thus delaying the collection periods.

The Hampshires, Shropshires, and So'ithdo^ms ejaculated ap-
proximately 1 cc. per collection. The average column of the ejac-
ulates vrere 1.073 » •993 » and .965 respectively. An analysis of
varir.iiCG was calculated for semen volume as described in Snedo-
cor(8). There was no significance found between breeds and within
breeds.

The analysis of variance of semen concentration (Table 3) re-
vealed no significance bet\^reen breeds, but there was a highly sig-
nificant difference between rams. This is shovm in the analysis
chart v;ith the f test stated at ^.^6 at the 5Jfa level. The f test
was 8.3^ for the number of sperm per cubic millimeter. There was
no significant difference between rams within the same breed fop
motility, but for the test betv/een breeds there was a very highly
significant difference, with the f test of 5.12. This shows that
there are some breeds with a higher semen motility than others.

Tatle 3» Analysis of variance.

D/P

S3

MS

Voluaw

Breed

Rams, Same Br.

Dates-RclSr.

Total

3

1.3^v

0M67

0.96
9.18

0.1920

0.2086

52

11.^8

2.33 Ins.
'..Ih Ins.

Breed

26.28

8.7600

Rams, Same Br.

i

15.92

3a8if0

Dates-Ro-^r.

16.79

0,3816

Total

52

58.99

2.75 Ins.
8.3^***

Breed

Ra&s, SajoB Br.

Dates-R<S:Br.

Total

3
52

61,71
21.06

17.68
100.^-5

20.5700
^.2120

^h,0l82

5.12**
Ins.

27

There were no analyses coEputed for libido because of the
very similar actions of rams studied. The numbers were also too
small to Justify analyses.

The ranking of the rams as for sperm concentration and aver-
age total number of sperm per ejaculation was as follows: (1) Suf-
folk (6,782 billion); (2) Hampshires (3.^391 billion); (3) South-
dov/na (2,8363 billion); and ik) Shropshires (1.7783 billion).

In suniiarizing the data for all breeds, the Suffolk was most
potent as a breeder in the sumEier months. The Haapshirea were
second and louthdowns third. This placed the Shropshires last ir-
respective of the one sterile ram.

28

Sroa-IARS AND CONCLUSIONS

The reproductive capacities of rams of different mutton
breeds (Suffolk, Hanpshire, Shropshire, and Southdovms) v/ore stud-
ied during the summer months. Most of the experimental data was
ottained in June or July; however, semen collections were made un-
til Septemher 1^, 1952# Three Hampshires, three Shropshires, two
Southdovms and one Suffolk were used in the experiment*

There were distinct differences among the mating desires of
rams of different breeds as well as bctiween rams within the sane
breed* The Suffolk* s and Hampshires' libido were i')ove that of
the Shropshires and Southdovjna on the average. The sterility of
one Shropshire did not appear to influence his sex desires.

There were no significant; differences in the production of
spern due to the effects of temperature during the extremely hot
period. The sperm number did not vary to a great extent as to in-
dividual spermatogenesis.

Itotility scores were similar for all ejaculates of individual
rams. There were three rams which varied more than tvro points on
their sperm activity scores. The Suffolk v/as most constant with
an "excellent" rating for each collection. The Hampshires were
second, Southdo\«s third, and the Shropshires were last. There
was a wide variation in No. 1 and 2 Hampshires and No. 1 South-
downs, Except for the No. 3 JIampshire, the last collection was
observed to have the highest motility rating during the entire
collection period.

29

The rams could be divided into two distinct groups for breed-
ing activity and semen quality. The Hampshires and Suffolk had
the highest ratings. The Shropshires and Southdo;ms were rated
somewhat lower than the tx^o other breeds. U'hen all scores were
considered on an equal basis, the breeds ranlced as follows i Suf-
folk, Hampshires, Southdowns, and Shropshires.

Late lambing from summer l;r3eding did not appear to cause an
inability of the rams to breed the ewes.

There are also indications that Suffolk and Hampshire rams
may be more active and reliable breeders during the summer months.

ACKUOV/LBDGEllEKT

The author wishes to express his Indebted thariks to
Dr# T. Donald Eell, Head of the Sheep Departnent, Animal Hus-
bandry, for the aid and direction of this erpericient .

For the careful guidance of the construction and criticism
of the manuscript, the writer extends his gratitude to Dr. Bell
and also Le-v/is A, Holland ana Vfelter H, Smith, Assistant Pro-
fessors in Animal Husbandry*

Acknov/ledgement is given to Tliomas Dean, Shepherd, K* S, C
for his aid in preparation and collection of the data.

3X

LITF.nATTjRE CITED

(1) Bergman, H. D., and L. A. Hewitt.

Laboratory iianual for Experiment al Physiology.
Minneapolis! B'lrgesa, 19*;-0. l8 p.

(2) McKenzle, F. F., and V, R» Berliner ^

The Reproductive Gapacjuj of Rams, Mo. Agr.
Expt. St a. Hgs. Bui. 265. 1937.

(3) , and R. v/. Phillips.

Measuring Fertility in Hams. Am. Vet. Med. Asaoo.
81+1109-202. 193^«

(k) I'foore, C, R., and W. J. Quick.

The Scrotum as a Temperature Regulator for the
Testis. Am. Jour. Physiol. 68j70-79. 192^.

(?) Phillips, R. W,, and F. N. Andrews.

The Speed of Travel of Ram Spermatozoa.
Anat. Rec. 68:127-132. 1937.

(6) Rice, V. A,, and F. K. Andrews.

Breeding and Improvement of Farm Animals.
hth ed. Kew York: McGraw-Hill, 1950.

(7) Schott, R. G., and R. W. Phillips.

The Rate of Sporm Travel and Tiuie of Ovulation
in Sheep. Anat. Rec. 79 » 531-5^. iM,

(8) Snedecor, G. W,

Statistical Methods, ^th ed. Iowa State College
Press. 19M-6.

APPERDIX

33

APPEi®IX

I)at9

Volume

no/mm3

Total

June 12

June 2^

July 12

July 22
Aug • ^-

Aug. 2h

Sept* l^f

Total
5

Ilampshire I

1,00 hM

1.50 3.85

1.50 3.26

1.00 3.70

2.00 2.18

1.00 2.58

.75 2.91

8.75 22.93

1.25 3.27

.775
uC90
3.700
2.580
2.580
2.182

27.937
3.991

June 12

June 25

July 2

July 12

July 22

Aug. k

Aug. 2k

Sept. 1^

Total

mm

X

Hampshire II

1.50 3.51

1.00 3.00

1.00 3.00

1.00 3.50

1.00 3.56

1.50 3.50

1.00 2.91

1.00 3.10

9.00
1.125

26.08
3.26

5.265
3.000
3.000
3.500
3.560
5.250
2.910
3.100

29.585
3.698

ko

5

June 12
June 25
July 22
Aug. k
Aug . 2^-
Sept. 1^

Total
I

1.50

.75

1.00
.66

.75
.50

5.16
.86

Hampshire III

2.80

2.77
3.10
2.67
2.17

17.356
2.892

5.760

2.100
2.776
2.0if6
2.002
1.085

15.769
2.628

h

3
2

3

21

3.5

Date

Volume No/Dan3
(99 1), J'^XlXm

Total

SaTfolk

1 p

h-

July-

1.2

1.50

6.750

5

July

22

2,00

^.10

8.200

1

Aug •

k

Total

6.5

16.72

27.130

20

5

1.62?

^.18

6.782

5

Southdovjn I

June

Ik

1.50

2.78

^.170

2

June

25

.75

3.00

2.250

3

July

2

1.00

4.10

l+.lOO

3

July

12

1.00

3.66

3.660

3

Aug,

.75

3.50

2.625

2

Aug.

21+

1.00

3.05

3.050

5

Total

7.00

23.19

22.955

21

1.00

3.312

3.179

3

Southdown II

June 25 1.00 1.50 1.500 2

July 2 .66 ^.00 2.66M- 2

July 12 2.50 2,25 5.625 3

July 22 .50 1.76 .880 2

Aug. 2 .63 2.10 1.323 2

Aug. 2h 1.00 3.01 3.010 3

Sept. 1^- .50 2.90 1,450 3

Total 6.79 17.52 17.^5 17

2 .97 2,6^7 2,493

Volume Ilo/mm^ Total
(fffii.) '''llU9£i MLUSZI ?^1;lX:itiy

Shropshlra I

Jane
June
July

July

12

25
2
22

1.00
.50
.50

1.00

2.10

1.50
1.68
2.20

2.100

lo^

2.900

Total
X

3.00

.75

7M
1.87

^.V59

1.11

3
3
3
3

12
3

July 2

July 12

July 22

Aug. h

Total

.2!

.63

2.50
1.00

1.0637

Shropshire II

2. ^1

3. ^
2.71
3. BO

11.32
2.83

.603
2.125
^.075
2.850

9.653
2.^13

3
2

3
3

11
2.75

June 12
Juno 25
July 22
Aug.

Aug. 2h
Gept. 1^

Total

1.00
1.50
1.00

1.50

1.00
1.00

7,00
1.166

Shropshire III

1.35
1.75

1.51

1.350
2.625

I.Mk)

5.^1-15
1.805

X
1
1

1
1

1

6
I

SEMEN QUALITY MD LIBIDO OP RAJfS OP DIPPEREMT l-IDTTON BBEEDS

IH TliE SUJxiJJi^; MOOTS

by

TED H. DOME

B. S,, Olclahoma Agricultural and Mcch&nical College
Stillwater, Oklahoma, 1952

M ABSTRACT OP A MASTER'S THESIS

subnitted in partial fulfillment of the

requirements for the degree

MASTER OF SCEKCE

Department of Animal Husbandry

KAI"ISAS STATE COLIEGE
OF AGRICULTTTHE AiiD APPLIED SCISNCS

1953

Sheep producers in the United States are confronted with a
late lainhing problem. This means the lamhs are being dropped at
a time of year ;^en the breeders do not benefit from the economi-
cal advantages which occur. The factors are the highest seasonal
trend of market prices, being free from insects, and usage of ram
lambs for breeding, shoi^riLng, and selling which is noticed by those
who produce early lambs. To acquire these benefits, the ewes must
be bred in middle summer and early fall.

One of the purposes of this experiment was to investigate the
theory that rams are responsible for late lambing seasons with the
temperature of the summer months being the decisive factor. The
other purpose was to compare the reproductive potency of rams of
different breeds to enable the commercial breeder to select a breed
uhloh will help him secure a higher lambing percentage during the
early lambing season.

Nine rams, including three tlampshires, three Shropshires, two
Southdowns, and one Suffolk, were used in this experiment.

Semen samples were collected as often as possible between
June 2, 1952, and September 1^, 1952, The saraples were analyzed
for motility of sperm, number of sperm, and volume of semen. During
each collection performance, the activity and libido were cited.

The results indicated that these breeds of rams cnulU be sa-
tisfactorily divided into tivo groups according to their reproduc-
tive capacities in the summer months, the first group being the
Suffolk and Hampshire breeds with the highest abilities and the
Shropshires and Southdowns as the lovrer-scored group.

Tho Hampshire and Suffolk rams surpassed the Southdo^'Ois and
Shropshires in motility, number of sperm, and libido throiijhout
the experiment. The volume of semen per oolleotion was not signi-
ficant between breeds.

Therefore, the conclusions of the exi^eriment were tlmt the rama
do not seem to be responsible for the late lambing seasons, and the
Hampshire and Suffolk rams would probably benefit the commercial
producer to a greater extent for breeding in the sumiaer months.